I drank at least 2 protein shakes a day for around 6 months and didn't notice any extra weight. How many to drink all depends on the brand of the shake, they all have different scoop sizes ect so its best to read the label and just follow what that says.
Drinking the shakes should help to repair your muscles and ease the aching a bit, but in my experience that also comes with time, the more you go the less you will ache!
As far as creatine goes that's where you will see weight gain, unless you are dedicated to gaining muscle mass there isnt any point in taking any!
But yeah, protein especially lean protein as you said you have shouldn't make you put weight on unless your drinking way to much of it! In fact alot of the new liquid diets that are coming out, Herblife ect include a few protein shakes a day and they are designed for weight loss! so you should have no issues atall.
I hope I helped, if your a member of a gym make sure to speak to your instructors, they are usually extremely helpful and are under the impression that no question is a stupid question.